1. Field of the Invention
This invention relates to a system for electronically aligning the polarization of an antenna.
More particularly, this invention relates to a system for electronically aligning the polarization of a receive/transmit antenna to the polarization of a transmit/receive antenna communicating with the former.
As it is well known, the exploitations of computer networks and of the Internet network have been exponentially increasing in recent years. Many people utilize today the Internet network for exchanging data in many different fields of their business or for personal interests.
At present, the exploitation of large band data transmission services based upon use of satellite systems has become a real opportunity which is being extended from an experimental level to an operative condition thereby opening the way to relevant potential both economical and technical applications.
From a technological view point, the antenna represents an essential component. The interest in respect of ground terminals equipped with low cost antennas adapted to receive and to transmit signals from/to different satellites is, therefore, significantly increasing.
The more recent developments are related to technologies aimed at designing flat antennas adapted to operate in full duplex mode and provided both with receive functions and with transmit functions, in view of the fact that they are provided with a common antenna aperture.
A largely utilized antenna type in connection with which the technological research is being very rapidly developed is related to the flat array antenna systems, since they offer various advantages with respect to the reflector antennas commonly utilized today.
An antenna array is realized—as directly suggested by the same definition thereof—by an antenna assembly including a number of identical generally linearly or planar arranged antennas (namely arranged on a line or in a plane), having a common orientation. The individual component elements of these antenna arrays are generally fed with different amplitude and phase.
The main advantage of this technology consists in the possibility to obtain a readily configurable radiation diagram, by varying the amplitudes and the phases of the individual component antennas.
Furthermore, it is possible to design specific arrays aimed at achieving main lobes and their zeroes in desired positions. Among others, also programmable array antennas are known, capable to modify their own radiation diagram by modifying the feed of the individual component antennas of the array.
Antenna of this kind are particularly utilized in space applications where the material displacement of any single antenna or of an antenna array is often a very hard task to be carried out.
The antenna arrays also have among other advantages a compact outline and a more pleasant aesthetic effect. Their implementation in multiple layer construction also adds low manufacturing cost advantages and an easier integration possibility for the antenna electronics.
These characteristics make these antennas particularly attractive for mobile communications.
As it is well known to any person skilled in the art, if the polarization of the antenna of a transmitter and the polarization of the antenna of a receiver are not aligned (namely the horizontal and the vertical components are not aligned), the effectively useful distance for a connection is dramatically reduced. Therefore, it is necessary that the two concerned antennas: (i) always utilize the same polarization type; and (ii) their polarization directions be aligned.
In the technology as presently available, the alignment of the antenna polarization is completely obtained by mechanical azimuth and elevation rotations.
This orientation system, when an antenna array is utilized in the field of data transmission for mobile systems, generates various inaccuracies in the orientation of the antenna and consequently causes phase lags.
Due to this drawback, the presently available antenna arrays have strictly defined utilization limits, particularly for use in the field of DVB (Digital Video Broadcasting) transmissions.